How to Know if my email read it or not

Dim messageId = Guid.NewGuid()
        MsgBox(messageId.ToString)
        Dim deliveryProcessor = "http://localhost:3738/SendEMailx/SendEMailx/email-delivery.aspx"
        Dim imgTag = String.Format("<img src=""http://www.earabdirectory.com/Uploads/Classifieds/162/162Big.jpg"" alt=""xxxx"" />", deliveryProcessor, messageId)


        Dim mail As New System.Net.Mail.MailMessage()
        mail.To.Add(txtEmailReceiver.Text)
        mail.From = New MailAddress(txtSenderEmail.Text, "Murad Hamdan", System.Text.Encoding.UTF8)
        mail.Headers.Add("Disposition-Notification-To", txtSenderEmail.Text)
        mail.Subject = Convert.ToString(txtSubject.Text).Trim()
        mail.SubjectEncoding = System.Text.Encoding.UTF8
        mail.Body = Convert.ToString(txtBody.Text).Trim()
        mail.Body += imgTag
        mail.BodyEncoding = System.Text.Encoding.UTF8
        mail.IsBodyHtml = True
        mail.Priority = MailPriority.High

        Dim client As New SmtpClient()
        client.Credentials = New System.Net.NetworkCredential(txtSenderEmail.Text, MyPassword)
        client.Port = CInt(587) '587
        client.Host = txtSMTP.Text '"smtp.gmail.com"
        client.EnableSsl = CBool(0)
        client.Timeout = 2000000
        Try
            client.Send(mail)
        Catch ex As Exception
            MsgBox(ex.Message)
        End Try